Integral Liner and Venturi for Eliminating Air Leakage

ABSTRACT

A combustion liner assembly for a gas turbine combustor includes a plurality of fuel nozzles disposed circumferentially about a central axis of the combustor, and a venturi section disposed downstream of the fuel nozzles and connected to a head end of the liner assembly. The venturi section defines an annular throat area downstream of the fuel nozzles. A liner sleeve is connected to and commences at a downstream end of the venturi section. At least a portion of the venturi section serves as a liner upstream of the liner sleeve.

BACKGROUND OF THE INVENTION

The present invention relates to apparatus and methods for minimizing or eliminating dilution air leakage paths in a gas turbine combustor and, more particularly, the invention relates to apparatus and methods for managing dilution air leakage to achieve lower emission levels.

As is well known, significant products of combustion in gas turbine emissions are oxides of nitrogen, i.e., NO and NO₂ collectively called NOx, carbon monoxide CO, and unburned hydrocarbons as well as other particulates. Various systems have been proposed and utilized for reducing emissions. For example, water or steam injection into the burning zone of the gas turbine combustor, catalytic clean-up of NOx and CO from the gas turbine exhaust and dry low NOx combustors have been used in the past. Compressor discharge dilution air introduced into the liner sleeve of the combustor and transition piece has also been utilized to reduce emissions.

It would be desirable to substantially reduce or eliminate leaks so that air flow in more non-critical areas is conserved and made more consistent from can to can. Additionally, it would be desirable to substantially reduce or eliminate leaks so that air flow can be increased in usable areas in a more dispersed and even mixing through the mixing holes.

BRIEF DESCRIPTION OF THE INVENTION

In an exemplary embodiment, a combustion liner assembly for a gas turbine combustor includes a plurality of fuel nozzles disposed circumferentially about a central axis of the combustor, and a venturi section disposed downstream of the fuel nozzles and connected to a head end of the liner assembly. The venturi section defines an annular throat area downstream of the fuel nozzles. A liner sleeve is connected to and commences at a downstream end of the venturi section. At least a portion of the venturi section serves as a liner upstream of the liner sleeve.

In another exemplary embodiment, a method of reducing air flow losses between a venturi section and a liner sleeve of a combustion liner assembly in a gas turbine includes the steps of utilizing at least a portion of the venturi section as a liner upstream of the liner sleeve; and providing an annular weld at a joint between the venturi section and the liner sleeve and at a joint between the venturi section and a head end of the combustion liner assembly.

In still another exemplary embodiment, a combustion liner assembly for a gas turbine combustor includes a venturi section connected to a head end of the liner assembly via an annular weld, where the venturi section defines an annular throat area within the liner assembly; and a liner sleeve connected to and commencing at a downstream end of the venturi section, where the liner sleeve is connected to the downstream end of the venturi section via an annular weld. At least a portion of the venturi section serves as a liner upstream of the liner sleeve.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary cross-sectional view of one-half of a combustion liner assembly about a combustor center line;

FIG. 2 shows an embodiment with the venturi section serving as part of the liner;

FIG. 3 is an alternative design;

FIG. 4 shows another embodiment utilizing a connector;

FIG. 5 is a cross-sectional view of still another alternative embodiment; and

FIG. 6 is a cross-sectional view of yet another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, particularly to FIG. 1, there is illustrated a combustion liner assembly, generally designated 10, including a cap centerbody 12, a liner sleeve 14, a primary fuel nozzle cup assembly 16 and a venturi section 18. It will be appreciated that the combustion liner assembly 10 is cylindrical or annular in configuration about a centerline axis 20 and that a plurality of primary fuel nozzles 16 are spaced circumferentially one from the other about axis 20. A swirler 22 is shown as part of the cap centerbody 12. The liner sleeve 14 has an inlet including a plurality of circumferentially spaced apertures 24 which receive compressor discharge air from a plenum (not shown) between the combustion liner assembly and the combustion flowsleeve/casing. The venturi 18 comprises a prefabricated double walled annular structure disposed within the liner sleeve 14 and includes an inner liner/wall 26 and an outer liner/wall 28. The venturi 18 has a radial inward apex 30 which defines a throat area 32 with the center cap body 12. The inner and outer liners 26 and 28 of venturi 18 include inner and outer wall portions 34 and 36, respectively, which extend axially upstream and radially outwardly toward cup assembly 16. The wall portions 34 and 36 terminate in a pair of flanges 38 and 40, respectively, which are turned to extend in a generally axially downstream direction. The flanges may be secured to the liner sleeve 14 by rivets 42. In the prior art design, the outer liner 28 of the venturi section 18 is also secured to the liner sleeve 14 downstream of the venturi by a plurality of circumferentially spaced rivets 44. As best illustrated in FIG. 1, the liner sleeve 14 is recessed radially inwardly to overlay the outer liner 28 of venturi 18 forming essentially an indented band for securing the liner sleeve 14 and outer venturi sleeve 28 to one another.

It has been discovered that variations in the leakage paths of the dilution air supplied to the combustor have a significant effect on emissions and that these variations are a result of parts tolerances and assembly of the parts. For example, a primary leakage path of concern is between the liner sleeve 14 and the outer sleeve 28 of the venturi 18 in the area of the rivets 44. It will be seen that the compressor discharge air supplied to the annular plenum 46 from externally of the combustion liner via apertures 24 may leak past the riveted connection. Variations in leakage flow past the riveted joint, however, have been discovered with respect to various identical combustors, and consequently, emissions will vary. Those emissions resulting from leakage path flows heretofore have not been identified or controlled.

There is an additional leakage path for the dilution air flowing from plenum 46 into the space between the inner and outer venturi sleeves 26 and 28, respectively, via apertures 50 in the outer venturi sleeve 28. This additional leakage path passes between the flanges 38 and 40 of the inner and outer liners 34 and 36 respectively of venturi 18. While these flanges 38 and 40 in the past engaged each another and were riveted to the liner sleeve 14, a variable gap between the flanges and from combustion liner to identical combustion liner appeared, resulting in variable emissions from ostensibly identical combustors.

A further leakage gap appears between the liner sleeve 14 and the overlapped flanges 38 and 40 of venturi 18. These gaps have been demonstrated to vary between identically constructed combustors and hence result in leakage flows causing variable emissions. Also, it is important that the venturi throat area 32 must be maintained within pre-determined limits, notwithstanding the removability of the venturi from the liner sleeve for maintenance and service. It is also important that the throat area be maintained upon original manufacture of the venturi and liner sleeve and throughout the various service procedures performed on the combustor during its life.

FIGS. 2 and 5 show an exemplary embodiment with an integrated venturi section and liner that substantially reduces or eliminates leakage areas and leakage losses. As shown, the venturi section 18 is connected to a head end 62 of the liner assembly. Like the current design, the flanges 38, 40 of the wall portions 34, 36 extend in a generally axially downstream direction. In the embodiment shown in FIG. 2, however, in an area between the position at which an upstream end of the venturi section 18 is secured to the head end 62 and a downstream end of the venturi section 18, the liner sleeve 14 is removed. An annular weld 64 seals the joint between the upstream end of the venturi section 18 and the head end 62. Additionally, the downstream end of the venturi section 18 is connected to the liner sleeve 14 via an annular weld 66. In this manner, a portion of the venturi section 18 serves as a liner upstream of the shortened liner sleeve 14. This structure effectively integrates the venturi section 18 and the liner sleeve 14.

FIG. 3 shows a more complex design utilizing an expansion joint or slip joint 68 including a fork section 681 and a straight section 682. In this embodiment, the fork section 681 is integral with the head end 62 and venturi section 18. As a consequence, a leak path at the venturi section connection to the head end is eliminated. Cooling air is passed through apertures 69 in the straight section 682. If air leaks around the slip joint 68, then it has no affect on the performance of the combustor because air is already being allowed into the hollow venturi cavity from the apertures 69 in the outermost liner wall.

Yet another alternative embodiment is shown in FIG. 4. In this embodiment, a connector part 70, which is preferably a machined connector part, connects the venturi section 18 to the head end 62. As shown, in a preferred construction, the connector part 70 is Y-shaped including an end post 72 and a split end 74. The split end 74 is welded to the inner and outer walls of the venturi section 18, and the end post 72, which is thicker than the split end 74, is welded to the head end 62. With the connector part, a larger area of the combustion liner 14 is removed. Arrow A in FIG. 4 illustrates the axial length over which the liner is removed.

FIG. 6 illustrates yet another alternative embodiment. In this embodiment, all gaps and leak paths between the venturi section 18 and the head end 62 in between the venturi section 18 and the liner sleeve 14 are sealed via an annular seal, such as by brazing or the like. During assembly, the liner can be tipped upright to allow the braze material to wick into the gaps.

The described embodiments substantially reduce or eliminate air flow losses between the venturi wall and the liner wall. Elimination of air flow losses will allow more consistent air flow to be utilized in the fuel air mixture in the head end combustion zone rather than leaking air flow into direct stream. The simple constructions as described use similar parts and technology as is found in current designs. The embodiments are easy to manufacture and will produce a more repeatable air flow from can to can and will in turn help to create better fuel air mixture patterns than the current design while also lowering combustion emissions. The design substantially reduces or eliminates air flow leaks in areas between the venturi and the liner wall so that the air flow can be used in areas in a more dispersed and even mixing through the mixing holes than with the current design. The components can be used as control points to adjust air flow such that additional air flow by virtue of the reduced air flow losses can be utilized to lower emissions as well as lower variation from can to can.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

1. A combustion liner assembly for a gas turbine combustor, the combustion liner assembly comprising: a plurality of fuel nozzles disposed circumferentially about a central axis of the combustor; a venturi section disposed downstream of the fuel nozzles and connected to a head end of the liner assembly, the venturi section defining an annular throat area downstream of the fuel nozzles; and a liner sleeve connected to and commencing at a downstream end of the venturi section, wherein at least a portion of the venturi section serves as a liner upstream of the liner sleeve.
 2. A combustion liner assembly according to claim 1, wherein the liner sleeve is connected to the downstream end of the venturi section via an annular weld.
 3. A combustion liner assembly according to claim 1, wherein the venturi section is connected to the head end via an annular weld.
 4. A combustion liner assembly according to claim 1, further comprising a connector part that connects the venturi section to the head end.
 5. A combustion liner assembly according to claim 4, wherein the venturi section comprises a double wall structure including an inner wall and an outer wall, and wherein the connector part is Y-shaped including an end post and a split end, the split end being welded to the inner wall and the outer wall of the venturi section, and the end post being welded to the head end.
 6. A combustion liner assembly according to claim 5, wherein the end post of the connector part is thicker than the split end.
 7. A combustion liner assembly according to claim 1, wherein an upstream end of the venturi section terminates in a flange that is bent to extend axially in a downstream direction, wherein the flange is secured to the head end via a plurality of rivets, and wherein the flange is sealed via an annular weld.
 8. A combustion liner assembly according to claim 1, wherein all gaps and leak paths between the venturi section and the head end and between the venturi section and the liner sleeve are sealed via an annular seal.
 9. A combustion liner assembly according to claim 8, wherein the annular seal is brazed.
 10. In a gas turbine, a method of reducing air flow losses between a venturi section and a liner sleeve of a combustion liner assembly, the method comprising: utilizing at least a portion of the venturi section as a liner upstream of the liner sleeve; and providing an annular weld at a joint between the venturi section and the liner sleeve and at a joint between the venturi section and a head end of the combustion liner assembly.
 11. A method according to claim 10, further comprising utilizing additional air flow by virtue of the reduced air flow losses to allow more consistent air flow in a fuel-air mixture in the head end.
 12. A method according to claim 11, wherein the additional air flow is utilized to tune turbine emissions.
 13. A combustion liner assembly for a gas turbine combustor, the combustion liner assembly comprising: a venturi section connected to a head end of the liner assembly via an annular weld, the venturi section defining an annular throat area within the liner assembly; and a liner sleeve connected to and commencing at a downstream end of the venturi section, wherein the liner sleeve is connected to the downstream end of the venturi section via an annular weld, wherein at least a portion of the venturi section serves as a liner upstream of the liner sleeve. 